A sustainable and organic solvent-free strategy for nitrogen functionalisation of carbon materials is presented herein. The developed method avoids hazardous reagents and energy-intensive conventional treatments by employing aqueous solutions of benign nitrogen-containing inorganic salts (NH4NO3, NH4Cl, and (NH4)2CO3). As a proof of concept, nitrogen-doped activated carbons were prepared from both a commercial activated carbon (YP-50F) and a biomass-derived porous carbon. In all cases, nitrogen was successfully incorporated into the carbon matrix, yielding nitrogen contents and surface functionalities comparable to those obtained through traditional organic functionalisation routes. A life cycle assessment demonstrates the clear environmental advantages of the proposed aqueous-based process, with a reduction of up to 90% in several impact categories compared to organic solvent-based methods. The electrochemical evaluation of the resulting nitrogen-doped activated carbons as supercapacitor electrodes confirms the validity of the approach. The nitrogen-doped activated carbons exhibit enhanced energy density and cycling stability compared to pristine activated carbons, and their performance is comparable to that of materials produced via organic solvent routes. This study establishes a greener and scalable pathway for nitrogen doping of carbon materials, highlighting the potential of simple aqueous chemistries to replace conventional, less sustainable functionalisation strategies.

In order to make the ammonia synthesis process more sustainable and facilitate its coupling with renewable energies, it is first imperative to carry out this reaction at lower temperatures, which requires new catalysts showing high activity (i.e., low activation energies) and proper kinetic characteristics (e.g., resistance to H2 and NHx poisoning) while operating at these temperature conditions. While Ru presents high activity in this reaction, it suffers from strong hydrogen inhibition, which is particularly important at low temperatures. The use of promoters such as cerium oxide can mitigate this issue taking advantage of metal-support interactions generated upon reduction treatments (e.g., electron donation and the formation of new oxygen vacancy sites). However, lab-synthesized ceria materials usually present low surface areas, thereby limiting the generation of oxygen vacancies and the ammonia synthesis activity as a result of weak metal-support interactions. With the aim to overcome this issue, we prepared, by a simple impregnation method, high surface area ceria- and ceria-alumina-supported Ru catalysts with improved ammonia synthesis performance at moderate temperatures. In this sense, lab-synthesized Ru/CeO2 (with higher specific surface area and lower crystallinity than commercial ceria) showed stronger metal-support interactions than the commercial sample, which resulted in a superior global ammonia synthesis kinetic mechanism with more positive hydrogen reaction orders (i.e., more resistant to hydrogen inhibition) and significantly lower activation energies (46 vs 61 kJ mol-1). We found that the use of alumina as structural support increased the surface area of ceria, thereby promoting the Ru-CeO2 interaction and the catalytic performance. We analyzed the effect of the surface chemistry of two different commercial aluminas (acid and basic) with similar surface areas. Basic alumina was found to increase the specific surface area of the catalyst to a larger extent as compared to acid alumina. Thus, the Ru/CeO2-Al2O3 catalyst with a 50 wt% of basic alumina showed an ammonia synthesis activity of 1.9 mmol g h -1 at 400 °C and ambient pressure and an activation energy as low as 44.8 kJ mol-1.

Flow electrode capacitive deionization (FCDI) is a desalination technology employing flowable carbon slurries to remove salt from an influent through the electro-sorption of ions at the surface of pores of activated carbon particles. This study presents an extensive morphological, electrochemical and rheological analysis of flow electrodes prepared using commercial (YP50F, YP80F, Norit, PAC) and lab-synthesized (KUA, PAC-OX) activated carbons. Simultaneous optimization of particle size, surface area, and surface chemistry of activated carbons is essential to enhance desalination efficiency in FCDI applications. The lab-made highly microporous activated carbon (KUA), prepared from a Spanish anthracite, exhibited a remarkably high specific surface area (~2800 m2/g) but required first a particle size reduction through ball milling (from 56 μm to 12 μm) for the respective flow electrodes to achieve flowability. The slurry of milled fine KUA (designated as KUAsingle bondF) shows a specific capacitance of 55 F/g, a 38-fold increase compared to its pristine form. The KUA-F flow electrode also achieved a maximum salt adsorption capacity of 185 mg/g, outperforming the leading commercial alternative (YP80F) by 26 %. The FCDI cell with the KUA-F flow electrode exhibited a desalination efficiency of 79 % at 15 wt% loading, surpassing YP80F by 29 %. In contrast, using PAC-OX (oxidized form of PAC), despite increasing oxygen functional groups and with relatively higher specific surface area, led only to a 2 % improvement in desalination performance, highlighting that oxidation alone at larger particle sizes and broader distribution is insufficient.

This review intends, in a critical way, the comprehensive view of the importance of porous carbons surface chemistry for their applications in an energy–environment nexus. Surface chemistry is presented as a combination of functional heteroatom-containing groups, dopants, and structural defects. First, we briefly address carbon surface chemical environment and the methods of its modification and characterization, indicating their practical limitations. Then, the effects of surface chemistry on separation, catalysis, energy storage, sensing and microwave absorption are introduced. Besides a critical analysis of published findings on these topics, we also include our views on the advancement in the processes which rely on porous carbons surface chemistry, and identify strategic areas and directions that should deserve further attention. We focus on new findings and important original contributions to the field. Since the community of carbon researchers grows following the strategic application of these materials, the role of functional groups, dopants and structural defects in various cutting-edge applications is emphasized, showing the progress in the field and the evolution of findings. A clear determination of the effects of carbon surface is often a challenge since carbons porosity and the locations of specific bonds/sites/defects in the carbon texture provide nanoconfinement effects.

The design of ammonia synthesis catalysts that are both scalable and kinetically efficient remains a major challenge for decarbonizing chemical production. Here, we report a series of Ru/CexLa1-xOy catalysts synthesized via a simple impregnation method, using only air-stable rare-earth oxides. Among them, the optimum Ru/Ce0.5La0.5Oy catalyst displays an ultra-finely dispersed Ru phase supported on a Ce–La solid solution with a high density of oxygen vacancies. Under mild conditions (400 °C, 0.1 MPa), this system delivers a remarkably low apparent activation energy (34.1 kJ mol−1), outperforming many state-of-the-art more complex hydride or intermetallic catalysts. Additionally, the catalyst exhibited a strongly positive dependence of the reaction rate on pressure, making it particularly well suited for operation at moderate pressures (2–3 MPa) typically delivered by PEM electrolyzers for hydrogen. These findings position Ru/Ce0.5La0.5Oy as a rare example of a simple, stable catalyst combining the favorable kinetic behavior of more complex Ru systems with the scalability and robustness demanded by renewable-based decentralized ammonia synthesis.